Large, critical-sized tissue defects (e.g., craniofacial, spinal, hip, and knee defects) comprising bone, vasculature, and cartilage damage caused by traumatic injury, cancer, or disease, may be challenging to treat owing to the size and complexity of the defects. Surgically implanting scaffolds and/or other forms of graft materials to promote tissue regeneration (e.g., bone and/or osteochondral regeneration) is a common approach in promoting tissue growth. Common sources of tissue grafts include autografts, allografts, and synthetic materials. Autologous and allologous sources are favored for their biocompatibility and minimized probability of disease transfection. However, several limitations exist including inadequate amounts of available autologous donor tissue and donor site morbidity. In addition, the amount of cadaveric donor tissue available from reserves is in limited supply.
In order to address such issues, metallic and synthetic materials, which closely match the mechanical properties of native tissue, have been adopted for large tissue defect repair. Current materials in use include metals such as titanium, cobalt, and stainless steel, as well as nonmetallic materials like hydroxyapatite, bioactive glass, or polymers. Metallic implants, though widely used as implantable fixtures due to their mechanical properties, often lead to pathological tissue deterioration as a result of corrosion. While some metallic implants have been modified for enhanced biocompatibility, they have also been found to release toxic ions deleteriously affecting local tissue. In an effort to address these concerns, nonmetallic synthetic materials, such as hydroxyapatite, have been employed due to their biocompatibility and manufacturability in the fabrication of porous three-dimensional (3D) structures. Although most inorganic ceramics exhibit effective bioactivity, the mechanical properties are inadequate for regeneration of native tissue. In addition, they can be difficult to process and manufacture.
Accordingly, there may exist a need for tissue engineering scaffolds made from a combination of biocompatible synthetic polymers and morphogenic factors in order to mimic the mechanical properties of native tissue and promote high levels of host-implant integration.